On 04/01/2017 09:48 AM, Dan Allen wrote:
Hi Bill,
I agree, however when the print is quite complex it makes the GUI very
unresponsive.
Painting into an off screen image is not GUI related. The print preview could
show something like "Generating Preview" while a background thread generates it
and then show it when it's ready for example. This would prevent the GUI from
seeming unresponsive to the user. I wasn't sure if there was a current method to
do something like this.
Yes. We agree that the actual printing is non GUI, but if you want
to show a print preview or progress meter, that is GUI and needs
to stay in the main thread.
So, something like:
- Create a progress meter dialog.
- Start your printing in a sub thread.
- The main thread waits, perhaps in a sub-QEventLoop, servicing events.
- After a few seconds, if printing has not completed, show the dialog.
- The sub-event loop monitors the printing process with a thread safe
communication mechanism, like signals and slots.
- When the printing completes, close the dialog.
- Exit your sub-event loop.
Thanks,
Dan Allen.
On 01/04/17 13:43, william.croc...@analog.com wrote:
On 04/01/2017 03:41 AM, Dan Allen wrote:
Hi,
Could anyone tell me if it's possible to paint into a QPrintPreviewWidget in
another thread, and if so, how?
I have created a class to perform printing and this runs in another thread.
When used for printing it works fine. However when used for the print preview,
nothing is shown unless I force the signal to either Qt::DirectConnection (i.e.
use the GUI thread) or Qt ::BlockingQueuedConnection (i.e. block the GUI
thread).
Dan:
Conventional wisdom, if not the rule of law, states that all GUI activity
should be done from the main thread. You may just be experiencing
the Qt library enforcing this rule.
Bill
Thanks,
Dan Allen.
_______________________________________________
Interest mailing list
Interest@qt-project.org
http://lists.qt-project.org/mailman/listinfo/interest
_______________________________________________
Interest mailing list
Interest@qt-project.org
http://lists.qt-project.org/mailman/listinfo/interest
_______________________________________________
Interest mailing list
Interest@qt-project.org
http://lists.qt-project.org/mailman/listinfo/interest
_______________________________________________
Interest mailing list
Interest@qt-project.org
http://lists.qt-project.org/mailman/listinfo/interest
